211099991 has 4 divisors (see below), whose sum is σ = 211191912. Its totient is φ = 211008072.

The previous prime is 211099949. The next prime is 211100009. The reversal of 211099991 is 199990112.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 211099991 - 2¹⁰ = 211098967 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (211099391) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 42425 + ... + 47138.

It is an arithmetic number, because the mean of its divisors is an integer number (52797978).

Almost surely, 2^211099991 is an apocalyptic number.

211099991 is a deficient number, since it is larger than the sum of its proper divisors (91921).

211099991 is an equidigital number, since it uses as much as digits as its factorization.

211099991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 91920.

The product of its (nonzero) digits is 13122, while the sum is 41.

The square root of 211099991 is about 14529.2804708286. The cubic root of 211099991 is about 595.4282076320.

The spelling of 211099991 in words is "two hundred eleven million, ninety-nine thousand, nine hundred ninety-one".